sortedArrayUsingComparator in sorting array contains object with 2 numbers

Question

iam trying to sort a object with 2 numbers using the api sortedArrayUsingComparator

array1= [array sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {

    person *p1 = (person*)obj1;
    person *p2 = (person*)obj2;

    if (p1.value>p2.value && p1.age>p2.age)
    {
        return (NSComparisonResult)NSOrderedAscending;
    }
    else
        return (NSComparisonResult)NSOrderedDescending;
}];

i want to make code to sort something like this ,,,,

input : 0  1
        1  2
        0  9
        1  4
        2  3

output: 0  1
        0  9
        1  2
        1  4 
        2  3

user529758 · Accepted Answer · 2013-09-02 14:52:03Z

14

Please don't cast id to person *. The type id is implicitly compatible with any Objective-C object type, so the cast is useless and it only decreases readability.
Also, class names should begin with a capital letter. Better name your class Person, not person.
The actual problem is somewhat similar to lexicographic sorting:

NSArray *sorted = [unsorted sortedArrayUsingComparator:^NSComparisonResult(id lhs, id rhs) {
    Person *p1 = lhs, *p2 = rhs;

    if (p1.value > p2.value) {
        return NSOrderedAscending;
    } else if (p1.value < p2.value) {
        return NSOrderedDescending;
    } else {
        if (p1.age > p2.age)
            return NSOrderedAscending;
        else if (p1.age < p2.age)
            return NSOrderedDescending;
        else
            return NSOrderedSame;
    }
}];

answered Sep 2, 2013 at 14:52

user529758

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6 Comments

Nikolai Ruhe Over a year ago

1. Please don't use the comma operator ever.

Nikolai Ruhe Over a year ago

2. Using proper parameter types for the block removes need for secondary variables altogether.

user529758 Over a year ago

@NikolaiRuhe 1. I haven't used the comma operator anywhere. 2. But then the block wouldn't be of a compatible type. (Try it, you will get a compiler error.) I'd prefer that if it was legal. 3. Thanks.

Nikolai Ruhe Over a year ago

1. OK, wrong term, you can keep your declaration separator. 2. The block would be of compatible type (no compiler warning in current clang when using (Person *lhs, Person *rhs), with -Weverything).

user529758 Over a year ago

@NikolaiRuhe 1. Thanks! 2. So rather I should try it. (And GCC was wrong then. Would you happen to know if the C rule for compatible function types does not apply to blocks? It seems so...)

|

Joe · Accepted Answer · 2013-09-02 15:04:26Z

5

I would recommend sorting with NSSortDescriptors:

NSArray *sortdesc = @[
                      [NSSortDescriptor sortDescriptorWithKey:@"value" ascending:YES],
                      [NSSortDescriptor sortDescriptorWithKey:@"age" ascending:YES]
                     ];
NSLog(@"%@", [array sortedArrayUsingDescriptors:sortdesc]);

answered Sep 2, 2013 at 15:04

Joe

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